This invention relates to a lift truck, and particularly to a lift truck capable of being used with a clamping apparatus for grasping a load from two or more sides.
A lift truck is a self-propelled vehicle equipped with a movable frame, referred to as a carriage, which can be raised and lowered along an upright mast. Various attachments, such as forks or clamps for supporting or grasping a load, can be mounted on the carriage so that the lift truck can raise and lower the load.
The carriage of a lift truck is usually equipped with rollers which roll along the inside of channels forming the mast. The engagement between the rollers and the channels enables the channels to resist forces acting on the carriage in the fore-and-aft direction of the lift truck, or moments acting on the carriage about an axis extending in the widthwise direction of the lift truck (such as can result from a load disposed in front of the lift truck). However, the channels have a much smaller ability to resist forces acting on the carriage in the widthwise direction of the lift truck, or moments acting on the carriage about an axis extending in the fore-and-aft direction of the lift truck (such as can result when a load being supported by the lift truck is spaced in the widthwise direction from the centerline plane of the lift truck, which is a vertical plane extending in the fore-and-aft direction of the lift truck and running through the widthwise center of the lift truck). Such a widthwise force or moment can cause the wheels of the carriage to be pressed against the channels or to become misaligned with the channels of the mast, making it difficult for the carriage to travel smoothly up and down the mast. In addition, because the rollers are typically made of a hard material such as steel, the misalignment can cause the rollers to gouge the channels, resulting in damage to the rollers and/or the channels.